Interactions of two cytotoxic organotin(IV) compounds with calf thymus DNA

The reactions with DNA of two antitumor active organotin(IV) compounds, the dimer of bis[(di-n-butyl 3,6-dioxaheptanoato)tin] (C52H108Sn4O1. 2H(2)O), compound 1, and tri-n-butyltin 3,6,9-trioxodecanoate (C19H4OSnO5.1/2H(2)O), compound 2, were analysed by circular dichroism, DNA melting experiments a nd gel mobility shift assays. It is found that both complexes modify only s lightly the B-type circular dichroism spectroscopy (CD) spectrum of calf th ymus DNA. On the other hand, both complexes were found to affect significan tly the parameters of the thermally induced helix-to-coil transition. Addit ion of 1 or 2 to calf thymus DNA samples does not favor DNA renaturation af ter melting ruling out formation of interstrand crosslinks. Moreover, the e ffects of both compounds on plasmid DNA gel mobility were investigated. Fro m the analysis of the present results it is inferred that both organotin(IV ) compounds do interact with DNA, probably at the level of the phosphate gr oups. (C) 2001 Elsevier Science BV All rights reserved.